Process for preparing an olefinic hydrocarbon mixture

ABSTRACT

In a process for preparing an olefinic hydrocarbon mixture comprising at least 5% by weight of mono-olefin oligomers of the empirical formula: 
 
C n H 2n  
 
where n is greater than or equal to 6, a feedstock comprising n-butene and propylene in a molar ratio of about 1:0.01 to about 1:0.49 is contacted under oligomerization conditions with surface deactivated ZSM-23. The resultant mono-olefin oligomers comprise at least 20 percent by weight of olefins having at least 12 carbon atoms, wherein said olefins having at least 12 carbon atoms have an average of from about 0.8 to about 2.0 C 1 -C 3  alkyl branches per carbon chain.

FIELD

This invention relates to a process for preparing an olefinichydrocarbon mixture.

BACKGROUND

Long chain olefins (C₁₀+) are important starting materials in theproduction of sulfonate surfactants, in which the olefins are used toalkylate aromatic hydrocarbons and the resultant alkyl aromatics aresulfonated to produce alkylaryl sulfonates. In addition, the alcohols oflong chain olefins have considerable commercial importance in a varietyof applications, including detergents, soaps, surfactants, and freezepoint depressants in lubricating oils. In such applications, the degreeand the position of the branching along the carbon chain of the olefinis often critical to the properties of the end product. Thus, forexample, highly branched olefins tend to produce surfactants with poorbiodegradability, whereas substantially linear olefins tend to producesurfactants with poor hard and cold water cleaning properties. Inaddition, it is found that lightly branched olefins, where the branchingis at the odd-numbered positions in the carbon chain, producesurfactants with enhanced biodegradability as compared to similarolefins where the branching is at the even-numbered positions in thecarbon chain.

One potential route for the production of long chain olefins is by theoligomerization of lower (C₂ to C₆) olefins, typically using an acidiccatalyst, such as a zeolite. Thus, for example, it is known from U.S.Pat. Nos. 3,960,978, 4,150,062; 4,211,640; 4,227,992; and 4,547,613 tooligomerize lower olefins over ZSM-5, but the resultant oligomers areessentially linear.

U.S. Pat. No. 5,026,933 describes a process for producing high molecularweight, slightly branched hydrocarbon oligomers from a lower olefinfeedstock employing a shape selective crystalline silicate catalyst,ZSM-23, which has been surface deactivated. The resultant oligomermixture comprises at least 20% by weight of olefins having at least 12carbon atoms and said olefins having at least 12 carbon atoms have anaverage of from 0.8 to 2.0 methyl branches per carbon chain. The lowerolefin feedstock employed is either propylene or n-butene.

Further investigation of the process described in the '933 patent hasnow shown that, whereas oligomerization of n-butene produces oligomersin which the majority of the branching appears to be at the odd-numberedpositions, such as the 3- and 5-positions, in the carbon chain,oligomerization of propylene produces oligomers in which the majority ofthe branching appears to be at the even-numbered positions in the carbonchain. Surprisingly, it has also been found that oligomerization ofmixtures of n-butene and propylene at molar ratios up to 1:0.49 producesoligomers in which the position of the branching appears to be similarto that obtained with butene alone, i.e., apparently concentrated at theodd-numbered positions in the carbon chain. Since propylene is availablein large quantities in a modern integrated oil refinery, this discoveryprovides an important extension to the applicability of the process ofthe '933 patent.

SUMMARY

Accordingly, the invention resides in a first aspect in a process forpreparing an olefinic hydrocarbon mixture comprising at least 5 wt %,such as at least 20 wt %, for example at least 85 wt %, of mono-olefinoligomers of the empirical formula:C_(n)H_(2n)where n is greater than or equal to 6, said mono-olefin oligomerscomprising at least 20 percent by weight of olefins having at least 12carbon atoms, said olefins having at least 12 carbon atoms having anaverage of from about 0.8 to about 2.0 C₁-C₃ alkyl branches per carbonchain, said process comprising contacting a feedstock comprisingn-butene and propylene in a molar ratio of about 1:0.01 to about 1:0.49,under oligomerization conditions with surface deactivated ZSM-23.

Conveniently, said feedstock contains n-butene and propylene in a molarratio of about 1:0.05 to about 1:0.35.

Conveniently, the ZSM-23 has been surface deactivated with a stericallyhindered nitrogenous base, such as 2,4,6-collidine.

In a second aspect, the invention resides in a process for producing along chain alcohol mixture comprising contacting at least part of saidolefinic hydrocarbon mixture with carbon monoxide and hydrogen underhydroformylation conditions and in the presence of a hydroformylationcatalyst.

In a third aspect, the invention resides in a process for producing analkylaromatic compound comprising contacting an aromatic compound withat least part of said olefinic hydrocarbon mixture under alkylationconditions and in the presence of an alkylation catalyst.

In yet a fourth aspect, the invention resides in a process for preparingan alkylaryl sulfonate by sulfonating the alkylaromatic compoundproduced in accordance with said third aspect of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention provides an improved process for producingslightly branched, high molecular weight olefinic hydrocarbons byoligomerizing a lower olefinic hydrocarbon feedstock in the presence ofa surface-deactivated ZSM-23 catalyst. The use of such a catalyst allowsthe use of an olefin feedstock comprising a mixture of n-butene andpropylene apparently without significant reduction in the amount ofbranching at the odd-numbered positions in the carbon chain of theresultant oligomers.

The hydrocarbon feedstock used in the process of the invention comprisesn-butene and propylene in a molar ratio of n-butene to propylene ofabout 1:0.01 to about 1:0.49 and such as about 1:0.05 to about 1:0.35.In addition, the feedstock can contain low molecular weight, typicallyC₄-C₆, saturated hydrocarbons, which can act as a heat sink during theexothermic oligomerization process. In general, the feedstock cancontain up to 80 wt %, or more typically up to 50 wt %, of paraffins.

The oligomerization catalyst used in the process of the inventioncomprises ZSM-23 which has been surface deactivated, conveniently bytreatment with a sterically hindered nitrogenous base, such as atrialkyl pyridine compound, and preferably with 2,4,6-collidine(2,4,6-trimethyl pyridine, gamma-collidine). The surface deactivatingcompound should have a minimum cross-sectional diameter greater than theeffective pore size of the zeolite to be treated; i.e., greater than 5Angstroms. ZSM-23 and its characteristic X-ray diffraction pattern aredescribed in detail in U.S. Pat. No. 4,076,842, the entire contents ofwhich are incorporated herein by reference. In one embodiment, theZSM-23 employed in the catalyst has an alpha value of about 25 and acrystal size of less than 0.1 micron and is conveniently composited witha binder, such as alumina.

Suitable oligomerization conditions include a temperature of about 160°C. to about 250° C., such as about 190° C. to about 230° C., for exampleabout 210° C. to about 220° C.; a pressure in the range of about 500psig (3447 kPa (gauge)) to about 1500 psig (10342 kPa (gauge)), such asin the range of about 750 psig (5171 kPa (gauge)) to about 1250 psig(8618 kPa (gauge)), and a feed weight hourly space velocity (WHSV) inthe range of about 0.1 hr⁻¹ to about 4.0 hr⁻¹, such as in the range ofabout 0.2 hr⁻¹ to about 3.0 hr⁻¹, for example in the range of about 1.75hr⁻¹ to about 2.25 hr⁻¹.

Where surface deactivation is achieved by treatment with a trialkylpyridine compound, the feed to the oligomerization process includesadditional trialkyl pyridine compound so that the surface properties ofthe zeolite are maintained during the process. Further details of theoligomerization process can be found in U.S. Pat. No. 5,026,933, theentire contents of which are incorporated herein by reference.

The product of the oligomerization process of the invention is anolefinic hydrocarbon mixture which comprises at least 5 wt %, such as atleast 20 wt %, for example at least 85 wt %, of mono-olefin oligomers ofthe empirical formula:C_(n)H_(2n)wherein n is greater than or equal to 6 and wherein said mono-olefinoligomers comprise at least 20 wt %, such as at least 60 wt %, ofolefins having at least 12 carbon atoms and said olefins having at least12 carbon atoms have an average of from about 0.8 to about 2.0, such asabout 0.8 to about 1.3, C₁-C₃ alkyl branches per carbon chain.Conveniently, the olefins having at least 12 carbon atoms contain nobranches other than methyl groups and ethyl groups.

Despite the presence of propylene in the oligomerization feed, it isbelieved that at least 50% of the C₁-C₃ alkyl branches in theC₁₂+olefinic product of the present process are located at theodd-numbered positions in the carbon chain.

By fractionating the olefinic hydrocarbon mixture produced by theoligomerization process of the invention it is possible to produce oneor more olefinic fractions, for example a C₁₂ olefinic fractioncomprising at least 85% by weight of mono-olefins having 12 carbonatoms, said mono-olefins having a straight backbone chain of at least 10carbon atoms and an average of from about 0.8 to about 2.0 (such asabout 0.8 to about 1.3) C₁-C₃ alkyl branches per carbon chain.

Part or all of the olefinic hydrocarbon mixture produced by theoligomerization process of the invention is conveniently used in theproduction of long chain alcohols for application as, for example,detergents, soaps, surfactants, and freeze point depressants inlubricating oils. Typically this is achieved by hydroformylation, thatis, reaction with carbon monoxide and hydrogen, according to the Oxoprocess. Catalysts employed can be cobalt or rhodium which may bemodified with phosphine, phosphite, arsine or pyridine ligands, asdescribed in U.S. Pat. Nos. 3,231,621; 3,239,566; 3,239,569; 3,239,570;3,239,571; 3,420,898; 3,440,291; 3,448,158; 3,448,157; 3,496,203; and3,496,204; 3,501,515; and 3,527,818, the disclosures of which areincorporated herein by reference.

Typical hydroformylation reaction conditions include a temperature ofabout 125° C. to about 200° C., a pressure of about 2170 kPa to about32550 kPa (300 psig to about 4000 psig) and a catalyst to olefin ratioof about 1:5000 to about 1:1. The molar ratio of hydrogen to carbonmonoxide is usually about 0.5 to about 10, such as about 1 to about 2.The hydroformylation reaction typically produces an aldehyde which canthen be hydrogenated to generate the required alcohol product.

The hydroformylation process can be carried out in the presence of aninert solvent, such as a ketone, e.g., acetone, methyl ethyl ketone,methyl isobutyl ketone, acetophenone and cyclohexanone; an aromaticcompound, e.g., benzene, toluene and the xylenes; a halogenated aromaticcompound, e.g., chlorobenzene and orthodichlorobenzene; a halogenatedparaffinic hydrocarbon, e.g., methylene chloride and carbontetrachloride; a paraffin, e.g., hexane, heptane, methylcyclohexane andisooctane and a nitrile, e.g., such as benzonitrile and acetonitrile.

The catalyst ligand may be made of tertiary organo phosphines, such astrialkyl phosphines, triamyl phosphine, trihexyl phosphine, dimethylethyl phosphine, diamylethyl phosphine, tricyclopentyl (or hexyl)phosphine, diphenyl butyl phosphine, dipenyl benzyl phosphine, triethoxyphosphine, butyl diethyoxy phosphine, triphenyl phosphine, dimethylphenyl phosphine, methyl diphenyl phosphine, dimethyl propyl phosphine,the tritolyl phosphines and the corresponding arsines and stibines.Included as bidentate-type ligands are tetramethyl diphosphinoethane,tetramethyl diphosphinopropane, tetraethyl diphosphinoethane, tetrabutyldiphosphinoethane, dimethyl diethyl diphosphinoethane, tetraphenyldiphosphinoethane, tetraperfluorophenyl diphosphinoethane, tetraphenyldiphosphinopropane, tetraphenyl diphosphinobutane, dimethyl diphenyldiphosphinoethane, diethyl diphenyl diphosphinopropane and tetratrolyldiphosphinoethane.

Examples of other suitable ligands are the phosphabicyclohydrocarbons,such as 9-hydrocarbyl-9-phosphabicyclononane in which the smallestP-containing ring contains at least 5 carbon atoms. Some examplesinclude 9-aryl-9-phosphabicyclo[4.2.1]nonane,(di)alkyl-9-aryl-9-phosphabicyclo[4.2.1]nonane,9-alkyl-9-phosphabicyclo[4.2.1]nonane,9-cycloalkyl-9-phosphabicyclo[4.2.1]nonane,9-cycloalkenyl-9-phosphabicyclo[4.2.1]nonane, and their [3.3.1] and[3.2.1] counterparts, as well as their triene counterparts.

Alternatively, part or all of the olefinic hydrocarbon mixture producedby the oligomerization process of the invention can be used, eitheralone or in admixture with linear alpha-olefins, as an alkylating agentin a process for the selective alkylation of an aromatic compound (e.g.,benzene) with a relatively long chain length alkylating agent to producesubstantially linear phenylalkanes. The alkylation process is conductedsuch that the organic reactants, i.e., the aromatic compound and theolefinic hydrocarbon mixture, are contacted under effective alkylationconditions with a suitable acid catalyst. Suitable aromatic hydrocarbonsinclude benzene, toluene, xylene and naphthalene, with preferredcompounds being benzene and toluene.

In one embodiment, the catalyst is a homogeneous acid catalyst such as aLewis acid catalyst, for example aluminum chloride. Alternatively, thehomogeneous acid catalyst is a Brønsted acid catalyst, such as HF orphosphoric acid. Suitable alkylation conditions with a homogeneouscatalyst include a temperature of from about −10° C. to about 100° C., apressure of from about 100 kPa to about 2500 kPa (1.0 to 25atmospheres), a feed weight hourly space velocity (WHSV) of from about0.2 hr⁻¹ to about 10 hr⁻¹ and an aromatic compound to olefinichydrocarbon mixture mole ratio of from about 1:1 to about 15:1. Typicalreaction conditions include a temperature of from about 0° C. to about50° C., a pressure of from about 100 kPa to about 300 kPa (1.0 to about3.0 atmospheres), a feed weight hourly space velocity (WHSV) of fromabout 0.1 hr⁻¹ to about 0.5 hr⁻¹ and an aromatic compound to olefinichydrocarbon mixture mole ratio of from about 5:1 to about 10:1. Thereactants can be in either the vapor phase or the liquid phase and canbe neat, i.e., free from intentional admixture or dilution with othermaterial, or they can be brought into contact with the catalystcomposition with the aid of carrier gases or diluents such as, forexample, hydrogen or nitrogen.

In a further embodiment, the alkylation process is conducted in thepresence of a heterogeneous catalyst, such as a molecular sieve.Suitable molecular sieves include mordenite, particularly dealuminizedmordenite and other 6-7 Angstrom pore molecular sieves disclosed in U.S.Pat. No. 5,026,933, the entire contents of which are incorporated hereinby reference.

In one practical embodiment, the alkylation catalyst comprises amolecular sieve having an X-ray diffraction pattern including d-spacingmaxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom. TheX-ray diffraction data used to characterize said molecular sieve areobtained by standard techniques using the K-alpha doublet of copper asthe incident radiation and a diffractometer equipped with ascintillation counter and associated computer as the collection system.Materials having the required X-ray diffraction lines are sometimesreferred to as molecular sieves of the MCM-22 family and include MCM-22(described in U.S. Pat. No. 4,954,325), PSH-3 (described in U.S. Pat.No. 4,439,409), SSZ-25 (described in U.S. Pat. No. 4,826,667), ERB-1 isdescribed in European Patent No. 0293032, ITQ-1 is described in U.S.Pat. No. 6,077,498, ITQ-2 is described in International PatentPublication No. WO97/17290, MCM-36 (described in U.S. Pat. No.5,250,277), MCM-49 (described in U.S. Pat. No. 5,236,575) and MCM-56(described in U.S. Pat. No. 5,362,697). The entire contents of saidpatents are incorporated herein by reference.

The molecular sieve alkylation catalyst can be combined in conventionalmanner with an oxide binder, such as alumina, such that the finalalkylation catalyst contains between about 2 and about 80 wt % sieve.

With a molecular sieve catalyst, suitable alkylation conditions includea temperature of from about 0° C. to about 500° C., a pressure of fromabout 20 kPa to about 25000 kPa (0.2 to 250 atmospheres), a feed weighthourly space velocity (WHSV) of from about 0.1 hr⁻¹ to about 500 hr⁻¹and an aromatic compound to olefinic hydrocarbon mixture mole ratio offrom about 1:1 to about 20:1. The WHSV is based upon the weight of thecatalyst composition employed, i.e., the total weight of active catalyst(and binder if present). Typical reaction conditions include atemperature within the range of from about 100° C. to about 350° C., apressure of from about 100 kPa to about 2500 kPa (1 to 25 atmospheres),a WHSV of from about 0.5 hr⁻¹ to about 100 hr⁻¹ and an aromatic compoundto olefinic hydrocarbon mixture mole ratio of from about 4:1 to about15:1. Again, the reactants can be in either the vapor phase or theliquid phase and can be neat, i.e., free from intentional admixture ordilution with other material, or they can be brought into contact withthe zeolite catalyst composition with the aid of carrier gases ordiluents such as, for example, hydrogen or nitrogen.

The alkylation process of the invention produces an alkylaromatichydrocarbon mixture in which the alkyl side chains are lightly branchedand in which most of the aromatic species are located at the 2- or 3-position in the alkyl side chain. The alkylaromatic hydrocarbon mixtureis therefore particularly useful as an intermediate in the production ofalkylarylsulfonates, which are useful as detergents or surfactants.Processes for sulfonating alkylbenzenes are described in the U.S. Pat.No. 4,298,547, the entire contents of which are incorporated herein byreference. More particularly, alkylaromatic hydrocarbons may beconverted to alkylarylsulfonates by sulfonation of the aromatic ringwith sulfuric acid. The sulfonation reaction is well known in the artand is commonly carried out by contacting the organic compound withsulfuric acid at temperatures of from about −70° C. to about +60° C.Detailed descriptions of specific commercial processes abound in theliterature. See, for instance, pages 60-62 of INDUSTRIAL CHEMICALS,Third Edition, by W. L. Faith et al, published by John Wiley & Sons,Inc.

1. A process for preparing an olefinic hydrocarbon mixture comprising atleast 5% by weight of mono-olefin oligomers of the empirical formula:C_(n)H_(2n) where n is greater than or equal to 6, said mono-olefinoligomers comprising at least 20 percent by weight of olefins having atleast 12 carbon atoms, said olefins having at least 12 carbon atomshaving an average of from about 0.8 to about 2.0 C₁-C₃ alkyl branchesper carbon chain, said process comprising contacting a feedstockcomprising n-butene and propylene in a molar ratio of about 1:0.01 toabout 1:0.49 under oligomerization conditions with surface deactivatedZSM-23.
 2. The process according to claim 1, wherein said feedstockcontains n-butene and propylene in a molar ratio of about 1:0.05 toabout 1:0.35.
 3. The process according to claim 1, wherein said ZSM-23has been surface deactivated with a sterically hindered nitrogenousbase.
 4. The process according to claim 3, wherein said stericallyhindered nitrogenous base is 2,4,6-collidine.
 5. The process accordingto claim 1, wherein said oligomerization conditions include atemperature of about 190 to about 240° C.
 6. The process according toclaim 1, wherein said oligomerization conditions include a temperatureof about 200 to about 230° C.
 7. The process according to claim 1,wherein said oligomerization conditions include a temperature of about210 to about 220° C.
 8. The process according to claim 1, wherein saidoligomerization conditions comprise a pressure in the range of fromabout 500 psig (3447 KPa (gauge)) to about 1500 psig (10342 KPa(gauge)).
 9. The process according to claim 1, wherein saidoligomerization conditions comprise a pressure in the range of fromabout 750 psig (5171 KPa (gauge)) to about 1250 psig (8618 KPa (gauge)).10. The process according to claim 1, wherein said oligomerizationconditions comprise a weight hourly space velocity of from about 1.0hr⁻¹ to about 4.0 hr⁻¹.
 11. The process according to claim 1, whereinsaid oligomerization conditions comprise a weight hourly space velocityof from about 1.0 hr⁻¹ to about 3.0 hr⁻¹.
 12. The process according toclaim 1, wherein said oligomerization conditions comprise a weighthourly space velocity of from about 1.75 hr⁻¹ to about 2.25 hr⁻¹. 13.The process according to claim 1, wherein said olefins having at least12 carbon atoms have an average of from about 0.8 to about 1.3 C₁-C₃alkyl branches per carbon chain.
 14. The process according to claim 1,wherein said olefinic hydrocarbon mixture comprises at least 20% byweight of said mono-olefin oligomers.
 15. The process according to claim1, wherein said olefinic hydrocarbon mixture comprises at least 85% byweight of said mono-olefin oligomers.
 16. A process for producing a longchain alcohol mixture comprising contacting at least part of theolefinic hydrocarbon mixture produced by the process of any precedingclaim with carbon monoxide and hydrogen under hydroformylationconditions and in the presence of a hydroformylation catalyst.
 17. Aprocess for producing an alkylaromatic compound comprising contacting anaromatic compound with at least part of the olefinic hydrocarbon mixtureproduced by the process of claim 1 under alkylation conditions and inthe presence of an alkylation catalyst.
 18. A process for preparing analkylaryl sulfonate by sulfonating the alkylaromatic compound producedby the process of claim 17.